1. Field of the Invention
The present invention relates to saccharide which is phosphorylated (hereinafter, referred to as phosphorylated saccharide). More particularly, the present invention relates to a phosphorylated saccharide derivative which is a complex of phosphorylated saccharide and a protein or a peptide or to a phosphorylated saccharide derivative which is a conjugate of phosphorylated saccharide or a phosphorylated saccharide derivative and alkaline earth metal or iron.
The phosphorylated saccharide or phosphorylated derivative has the effect of inhibiting the precipitation (hereinafter, referred to as solubilization) of alkaline earth metal such as calcium or iron or has the effect of promoting the absorption of calcium. Accordingly, the present invention is useful as raw materials, compositions for foods and drinks, compositions to be added to foods, or raw materials or compositions for feeds which prevent various kinds of diseases by promoting the absorption of alkaline earth metal such as calcium or iron contained or allowed to be contained in foods, drinks, feeds, or fertilizers into a living body to improve health of a human or an animal.
The present invention also relates to a raw material and a composition for a fertilizer which promotes the absorption of calcium into plants or fruits to allow the plants or fruits to hold longer. Furthermore, the present invention also has the effect of preventing carious teeth. Specifically, the present invention can be added to oral compositions such as tooth paste, mouth wash, and troche, as well as foods, drinks, and feeds. The present invention can be used as a scale preventive capable of preventing or suppressing the generation of various scales, in particular, calcium scales and magnesium scales.
2. Description of the Related Art
Among nutrients to be taken from foods, minerals are indispensable for maintaining the function of bones, nerves, and muscle. However, in daily life, people are not likely to take sufficient minerals; therefore, the influence of insufficient absorption of the minerals on health has been raised as a problem.
For example, the average intake of calcium has not reached its required amount, which is set at a high level, such as 600 mg in Japan, because of low absorption ratio of calcium in a body. Thus, it is important to increase the absorption ratio of calcium in a body. The reasons why calcium is not likely to be absorbed in a body are as follows: calcium has been known to form an insoluble precipitation (i.e., calcium phosphate) by binding to inorganic phosphate in an alkaline region. The atmosphere in intestine is weak alkaline and recent processed foods contain a great amount of inorganic phosphate; therefore, calcium taken in a body becomes calcium phosphate to be precipitated. This prevents calcium from being absorbed through the intestine.
It is important to allow calcium to be efficiently absorbed through the intestine in the atmosphere thereof. In particular, growing infants and pregnant women need a large quantity of calcium. Furthermore, osteoporosis caused by insufficient digestion of calcium is also a serious problem. Osteoporosis is caused by a reduction in the ability of the intestine to absorb calcium which occurs with age. Examples of calcium-rich foods include dairy products such as milk, yogurt, and cheese; and dried products or food boiled down in soy of sea foods such as a sardine and a shrimp. In some cases, these foods are not likely to be taken in, because of preference and the decrease in masticatory power.
As for the ingestion of iron, divalent iron is likely to be oxidized to change to a trivalent iron. Oxidized iron coagulates in a neutral to alkaline region to form a precipitation, and hence becomes difficult to be absorbed by a living body. The absorption ratio of iron in a living body is greatly varied depending upon the food which contains the iron; thus, it cannot be said that the ingestion of iron by people of today who are likely to have an unbalanced diet is sufficient. Particularly, women are supposed to take in a considerable amount of iron; therefore, a low intake thereof causes a problem.
Magnesium phosphate, like calcium phosphate, is insoluble. The absorption ratio of magnesium in a living body is relatively low; therefore, insufficient digestion thereof, especially by growing infants and pregnant women, causes a problem. The absorption ratio of magnesium in a living body is also likely to vary depending upon the food which contains the magnesium.
Growing infants and pregnant women are unlikely to absorb sufficient amount of the above-mentioned minerals; therefore, they are required to take in much more of these minerals. Furthermore, recently, problems involving weight control and an unbalanced diet are getting serious. Thus, foods, especially luxury foods which allow iron and magnesium as well as calcium contained therein to be effectively absorbed by a living body are demanded, and it is important to develop an ingestion method for promoting the absorption of these minerals.
In the case where calcium, magnesium, iron, or the like is added to drinks for the above-mentioned purposes, precipitates are generated while they are kept, resulting in the loss of effective components. Furthermore, excess addition of calcium has been known to cause the decrease in utility of a protein (Goto et al., "J. Jap. Soc. Nutr. Food Sci." vol. 32, pp. 1-11, 1979) or the decrease in utility of minerals (Naito et al., "J. Jap. Soc. Nutr. Food Sci.", vol. 39, pp. 433-439, 1986).
In the livestock industry, the rapid growth of broilers, pigs, and the like has been demanded in an attempt to improve the productivity; however, their bones cannot catch up with such a rapid growth. As a result, the livestock end up having weak legs and being deformed. Calcium is added to foods or the like particularly for the purpose of strengthening bones, improving egg shells, reinforcing calcium in milk, and preventing the bending of eels' bones; however, a low utilization factor of calcium in animals causes a serious problem.
Calcium is also a very important element for plants. It has been known that the administration of chelate calcium such as EDTA-calcium strengthens cell walls or suppresses the generation of ethylene gas to retard aging and to improve the keeping quality (K. Tanaka et al., J. Japan. Soc. Hort. Sci., vol. 61, pp. 183-190, 1992). However, since EDTA-calcium has toxicity, the development of a chelating agent which is safe and effective has been desired.
A material capable of forming a compound together with calcium, which prevents calcium from being insolubilized in the atmosphere of the intestine to allow calcium to be efficiently absorbed through intestine, has been developed and utilized. For example, a technique of adding casein phosphopeptide (CPP) to drinks or foods (Japanese Laid-Open Patent Publication Nos. 3-240470 and 5-284939); a calcium solubilization effect of a complex of calcium citrate and calcium malate (Japanese Laid-Open Patent Publication No. 56-97248); and a bone strength enhancing effect of calcium pectate (Japanese Laid-Open Patent Publication No. 6-7116) have been known. These compounds have already been utilized partially for foods. However, the use of these compounds is limited depending upon the purpose; thus, they are not necessarily satisfactory.
For example, casein phosphopeptide has a great effect on the absorption of calcium, and therefore is comparatively often used for foods. This peptide constitutes lactoprotein contained in milk. However, the lactoprotein is contained in milk in a small amount and is not easy to fractionate; therefore, the lactoprotein is very expensive. Furthermore, products which are not sufficiently refined, in other words, those containing bitter peptides in addition to casein phosphopeptide are not preferable in terms of taste.
Acidic polysaccharide or acidic proteins have also been known to have the ability of forming a compound with calcium. These polysaccharide or proteins are macromolecules, which increase the viscosity when added to foods; therefore, their use is limited. Furthermore, organic acids such as malic acid and tartaric acid are cheap but exhibit unfavorable taste when added to foods. These organic acids also have a problem in terms of the health of teeth because they sometimes decalcify the enamelum of teeth.
Dentalis lapis and bacterial plaque have been known to cause gingivitis, periodontitis, or dental caries. Although the detail of the formation of dentalis lapis has not been clarified, the formation is considered as a calcification phenomenon that calcium or phosphorous supplied from saliva and exudate is deposited on organic substrates such as bacteria, which constitute plaque, and saliva glycoprotein, to be crystallized. As for existing dentalis lapis inhibitors, there are proposals by Miyake et al. (J. Japan. Soc. Periodent, vol. 30, No. 3, pp. 860-867) regarding sodium pyrophosphate or sodium tripolyphosphate. Caries are formed as follows: Streptococcus mutans (strain 6715) forms non-water-soluble glucan, using sucrose as a nutrient source, under action of enzyme, glycosyltransferase (hereinafter, abbreviated as GTase). Glucan which covers the surface of teeth causes bacterial plaque. When Streptococcus mutans is acid-fermented in the bacterial plaque, teeth start melting to form dental caries. As non-cariogenic saccharides, some oligosaccharides which do not become a nutrient source for Streptococcus mutans have been proposed. (S. Hamada et al., J. Jpn. Soc. Starch Sci., vol. 31, pp. 83-91, 1984). Furthermore, as cariostatic agents, polyphenol which is a component of tea has been reported and utilized (S. Sakanaka et al., Fragnance Journal, vol. 11, pp. 42-49, 1990). However, the use of polyphenol is limited, because it also involves a problem with taste. Accordingly, a material having an effect on both dentalis lapis and bacterial plaque has yet been developed.
In general, as properties of oligosaccharide, those related to low-calorie and function of preventing intestinal disorders have been reported in great number; however, those related to phosphorylated saccharide have not been reported.
Gelatinized starch has high viscosity. This is attributable to the fact that amylopectin in starch is a long chain molecule having a number of branches. In the case where maltose or cyclodextrin is produced using starch as a raw material, gelatinized starch is difficult to handle because of its high viscosity. For example, when gelatinized starch having a concentration at a certain level or more is transported through a pipe, the pipe will be clogged with the starch.
As described above, the characteristics (low solubility, retrogradation, and high viscosity) of existing starch limit the use thereof in foods and other fields. Under these circumstances, a study was conducted, for improving the solubility and retrogradation resistance of starch by subjecting starch to an enzyme treatment, a chemical treatment, or a physical treatment so that the starch degrades into smaller molecule; as a result, retrogradation of starch was suppressed to a certain degree. However, it is difficult to prevent an excess decrease in molecular weight and intrinsic characteristics of starch, which is originally a macromolecule, will be lost.
The generation of scales in various kinds of industrial water systems is a serious problem irrespective of whether it is a high-temperature water system or a non-high-temperature water system. For example, when a water system is heated, metal ions such as calcium and magnesium which are contained in the water system in a dissolved state are likely to change to insoluble compounds, and deposit as scales on the heat conducting surface which is in contact with the water system. This phenomenon noticeably occurs in high-temperature water systems such as a boiler, a desalting device, and a device for utilizing geothermal hot water, which causes the decrease in thermal efficiency, blocking of a water path, etc.
In most starches stored by plants, phosphate groups are partially bound by an ester linkage to glucose constituting starch. Although starch generally contains phosphate in a small amount, starch of potatoes, particularly white potato is likely to contain a relatively large amount of phosphoric acid (T. Yagi et al., Denpun Kagaku, vol. 20, p. 51, 1973). It has been known that a phosphate group is bound by an ester linkage to a glucose residue at the 3-position and 6-position thereof in potato starch (Y. Takeda et al., Carbohydrate Research, vol. 102, pp. 321-327, 1982). In the case where such starch is degraded with starch degrading enzymes such as amylase, the enzyme cannot act on the vicinity of a glucose residue where a phosphate group is bound by an ester linkage in potato starch. Thus, it has been known that phosphorylated saccharide remains without degradation at a time of the completion of saccharification. It has also been known that for this reason, phosphorylated saccharide is disposed of as a disposal without its composition being known in the starch saccharification industry for producing oligosaccharide, maltose, and glucose.
In the starch saccharification industry, the step of allowing a saccharide solution to pass through an ion exchange resin is used for the purpose of removing enzymes used for saccharification and remaining phosphorylated saccharide from the saccharified solution.
In the above step, phosphorylated saccharide adsorbed by the ion exchange resin is eluted therefrom when the ion exchange resin is washed with a sodium hydroxide solution for reproducing the resin. The solution containing phosphorylated saccharide after being washed has been disposed of as a liquid waste. Because of strong alkalinity, phosphorylated saccharide contained therein is decomposed to be phosphoric acid and neutral saccharide or a reduced end of the saccharide is oxidized; therefore, the phosphorylated saccharide in the liquid waste remains at a low rate.
On the other hand, starch (hereinafter, it may be referred to as chemically modified starch) to which a phosphate group is chemically bonded has been known. According to the standards of food additives in Japan, in the case where phosphorylated starch is used as a food additive, it is required that phosphorus bound to the starch be contained in an amount of 0.2 to 3%, and free inorganic phosphate which is not bound to the starch be contained in an amount of 20% or less, based on the total amount of phosphorus.
Studies regarding the formation of a compound or a complex of phosphorylated saccharide or chemically modified starch with alkaline earth metal such as calcium or iron; those regarding the promotion of the absorption of alkaline earth metal such as calcium and iron into a living body, using phosphorylated saccharide; and those regarding detergents and dentalis lapis inhibitors using phosphorylated saccharide have not been conducted.